1. FIELD OF THE INVENTION
The invention relates to tablets having a gelatin overcoat formed by spraying a low bloom gelatin and water solution onto a previously coated tablet, the gelatin coating imparting a low coefficient of friction and thus an increased slipperiness and swallowability to the tablet without the stickiness or thickness normally associated with gelatin type coatings. The invention also relates to a method of producing such tablets.
2. DESCRIPTION OF THE PRIOR ART
The pharmaceutical industry has long used empty gelatin capsules to encapsulate dosages forms of various medicines. Remington's Practice of Pharmacy, 17th Ed., p. 1625 to 1631. Recently, however, problems with tampering have caused a curtailment in consumer demand for capsule products. As a result, some producers have withdrawn their capsule products from the market and replaced them with pills, tablets or oblong shaped pills called caplets.
The coatings of pharmaceutical dosage forms such as pills or tablets utilizing rotating pan systems is well known. Typical coating processes include sugar coating which utilize coating powders such as sugar, acacia, flour, starch, are applied with an adhesive solution such as a viscous solution of acacia, gelatin or sugar and film coating which utilize film forming agents such as vinyl polymers, celluloses, acrylates, or natural gums and resins such as zein, gelatin, shellac and acacia. Remington, 17th Ed., p. 1623-1643.
In Japan patent No. 44-26677 to Daiichi Seiyaku Co. a method of manufacturing coated tablets is disclosed. Specifically the tablet is first undercoated with a first stage coating solution of 1 to 10 parts of a viscous substance such as gelatin, 30-70 parts of a solid filler such a titanium dioxide or talc and 48-60 parts of a solvent such as water. A heavy undercoat of approximately 170 mg is sprayed on in a coating pan apparatus followed by a second stage film coating of cellulose, vinyl resins of PEG. The method disclosed in the Japanese patent differs substantially from the novel coated tablet and method of the present invention because a solution of gelatin and solid filler is utilized as an undercoating. Such a solution, having a solid filler as a major component, would not impart a low coefficient of friction or slipperiness and swallowability to the tablets as would the solution of low bloom strength gelatin utilized in the present invention.
In U.S. Pat. No. 4,820,514, a method for coating a caplet with a gelatinous coating is described. The method so described involves dipping one end of the caplet and then the other end into a gelatinous solution to produce a coating having a thickness of about 5 to 40 mils (col 10 lines 56 to 60). The gelatin solution disclosed for use with this method includes a gelatin having a bloom strength from 150 to 270 bloom and may include other agents such as plasticzers, preservatives, color, opacifying agents, methylcellulose or polyvinyl alcohols. This patent also describes a failed attempt (col 2 lines 3 to 30) to coat caplets with gelatins using a coating pan system. The caplets so coated were said to have am insufficient coating thickness of only 6 mils and not to be as shiny as caplets coated by a dipping process. This patent thus teaches away from spray coating gelatin solution and would teach someone away from the coated tablet of the present invention having a low coefficient of friction and increased slipperiness and swallowability with less adhesion or tack. This patent also fails to recognize the beneficial effects of low bloom strength gelatin on the stickiness and thickness of the final product.
In Japanese 52-41213 to Freund Industrial Co., another coating application is disclosed. This patent discloses coating pills with a coating composition comprising low molecular weight gelatin, copolymer, titanium dioxide pigments, alcohol and water. Coating processes utilizing alcohol are not favored due to environmental restrictions. The tablets of the present invention do not utilize alcohol.
In U.S. Pat. No. 3,962,384 a spray drying or agglomorating system is described, in which emulsions of gelatin and vitamin E are sprayed. This patent discloses O bloom strength gelatins as the preferred gelatins. However, there is no teaching of using such gelatins for coatings. Nor is there any teaching or suggestion of the decreased coefficient of friction, increased slipperiness and swallowability imparted to previously film coated tablets by such gelatin. The gelatin is used in the situation described in this patent as a binder. Use of gelatin as a binder would not suggest that an overcoat of a low bloom gelatin would have decreased coefficient of friction.
In U.S. Pat. No. 4,702,919 a fluidized bed granulation method which includes spraying a binder solution which comprises 1-10% binder is described. Col 2 line 41 identifies gelatin as one of sixteen (16) suitable binders. Suitable solvents include water as well as organic solvents. At col. 2 line 60 it is described that a viscosity of 1 to 1000 cp, with 10 to 500 being preferred, is necessary for spraying.
In U.S. Pat. No. 4,816,259 types of gelatins suitable for producing soft gelatin capsules are described as 130-200 bloom alkali skin or bone type (col 2 line 26).
In U.S. Pat. No. 3,141,792 pan coating apparatus and standard compositions components are described. Coating-pan systems such as the "Vector-Freund Hi-Coaters", sold by Vector Corporation, 675 44th Street, Marion, Ia. or the "GC-1000, GC-1250 or GC-1750" sold by Glatt Air Techniques, 20 Spear Road, Ramsey, N.J. are well known. These coating pan systems include a rotating drum to hold the pills or tablets to be coated and an air-atomization and spray gun inserted into the center of the drum for spraying a mist of the coating material on the caplets, capsules or tablets.